Hi!
23-Авг-2006 16:11 [EMAIL PROTECTED] (Jason Hood) wrote to
[email protected]:
JH> I received a bug report about SHSUFDRV not working in FreeDOS, but
JH> it worked fine in MS-DOS; RDRV also worked fine. After failing to
JH> replicate the problem with the versions of FreeDOS I had, I finally
JH> got the latest boot CDs (beta9-sr2 & 1.0-testing). These did indeed
JH> fail, so I was able to offer that user a fixed FDRV.
JH> The problem itself is due to the SDA. It seems sometime between 2035a
JH> and 2036 the (temporary) DTA has moved into the SDA. This means that
JH> when FDRV reads a sector and then restores the swap data, the sector it
JH> just read gets overwritten with whatever was in the swap. The fix
JH> simply made the SDA size a fixed 0x7c0 bytes, thus preventing the
JH> overwrite. To provide a more desirable solution, what should I do?
Not sure, if I understand your problem, but what prevents you from
setting your own address of DTA (INT 21/1A)?
JH> 1) The SDA is unlikely to change, just leave it fixed at 0x7c0.
JH> 2) Buffer a single sector, write it back after the swap.
JH> 3) Provide a better size to the SDA function (215D06).
JH> 4) Move the DTA back out of the SDA.
JH> 5) Make use of the internal seek/read calls (2F1227/8).
JH> Of course, I would prefer 3 or 4, since that involves no effort
JH> on my part. :) 1 requires separate code for other DOSes (or I could
JH> just make it a fixed 0x7da, that MS-DOS 7.10 returns). 2 requires an
JH> extra 512 bytes for the buffer. 5 would probably be best (no swap
JH> required at all), but unfortunately ROMDOS does not support them, nor
JH> is there a write function (hence using the SDA in the first place).
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